Study A: We hypothesize that a different partitioning of leucine and lysine tracers, between fast and fed states, would generate data that would not compromise, significantly, our previous understanding and experimental findings that leucine and lysine requirements as defined by FAO/WHO/UNU (1985) are too low. Hence, we expect further support to the MIT-generated values of dietary IAA minimum requirements. Study B: We hypothesize that a decline in dietary IAAs (from "generous" [studied previously] to "intermediate" levels, at a constant total N intake of 160 mg N/kg/d, would not affect significantly leucine and lysine balances and requirements which would be expected to be similar to those described in our previous studies (MIT leucine requirement at 40 mg/kg/d, and lysine at 30 mg/kg/d).